The present invention relates to a dimerization of butenes containing isobutene to minimize a formation of 2,2,4-trimethyl pentenes.
Heretofore, it has been known to obtain dimers by a dimerization of n-butenes using each of various catalyst systems comprising a nickel salt and an aluminum compound.
However, it has been considered that if isobutene is included in the starting material of n-butene, tertiary carbon in isobutene is converted into carbonium ion by an aluminum compound whereby higher oligomers are produced. Even though the reaction is stopped in the stage of the dimerization by selecting the reaction conditions, the resulting C.sub.8 olefins include 2,2,4-trimethyl pentenes having quaternary carbon which cause inferior properties.
Accordingly, it has been considered to be necessary to remove isobutene in the dimerization of butenes or to separate a by-product formed from isobutene as high boiling point product after the dimerization of butenes.
The inventors have studied to various processes for a dimerization of isobutene with a dimerization of n-butene and have succeeded in reducing a formation of 2,2,4-trimethyl pentenes.